In general, a seat of a vehicle has, at a top of a seat back thereof, a headrest configured to support a head of an occupant from the rear. The headrest is brought as close as possible to the head of the occupant. Thus, when the vehicle is collided from behind, the headrest receives the head of the occupant from the rear to alleviate an impact, thereby being capable of preventing the occupant from suffering whiplash injury.
It is desired that the headrest of this type be fixed at a position as close as possible to a head of an occupant so that the impact caused by the collision on the vehicle can be alleviated. Meanwhile, when a head of an occupant is always held in contact with the headrest during driving, the occupant may have a feeling of discomfort. Thus, inplace of the above-mentioned fixed headrest, there has been proposed a movable headrest enabling positional adjustment with respect to a head of an occupant (see, for example, Patent Literature 1).
The movable headrest disclosed in Patent Literature 1 includes a headrest tilting mechanism in the headrest main body. The movable headrest is rotatable about a rotary shaft of the headrest tilting mechanism, thereby enabling positional adjustment of a headrest main body in forward and backward directions. In the movable headrest, the headrest main body includes a base gear arranged on a seat back stay side and a lock gear arranged on a headrest main body side. The headrest main body has a configuration in which a locking teeth of the lock gear are to be meshed with locking teeth of the base gear. A meshing position of the locking teeth of the lock gear with respect to the locking teeth of the base gear corresponds to a locking position of the headrest main body.